In a liquid crystal display device, a classification based on an operating mode for liquid crystal molecules includes a phase change (PC) mode, a twisted nematic (TN) mode, a super twisted nematic (STN) mode, an electrically controlled birefringence (ECB) mode, an optically compensated bend (OCB) mode, an in-plane switching (IPS) mode, a vertical alignment (VA) mode, a fringe field switching (FFS) mode and a field induced photo-reactive alignment (FPA) mode. A classification based on a driving mode in the device includes a passive matrix (PM) and an active matrix (AM). The PM is classified into static or multiplex and so forth, and the AM is classified into a thin film transistor (TFT), a metal insulator metal (MIM) and so forth.
A liquid crystal composition is sealed into the device. Physical properties of the composition are related to characteristics of the device. Specific examples of the physical properties of the composition include stability to heat and ultraviolet light, a temperature range of a nematic phase, viscosity, optical anisotropy, dielectric anisotropy, specific resistance and an elastic constant. The composition is prepared by mixing many liquid crystal compounds. The physical properties required for the compound include a high stability to an environment such as water, air, heat and light, a wide temperature range of a liquid crystal phase, a small viscosity, a suitable optical anisotropy, a large dielectric anisotropy and a good compatibility with other compounds. The compound having a high maximum temperature of the nematic phase is preferred. The compound having a low minimum temperature of the liquid crystal phase such as the nematic phase or a smectic phase is preferred. The compound having the small viscosity contributes to the device having a short response time. A suitable value of optical anisotropy is different depending on a device mode. The compound having a large positive or negative dielectric anisotropy is preferred for driving the device at low voltage. The compound having the good compatibility with other liquid crystal compounds is preferred for preparing the composition. The device may occasionally be used at a temperature below a freezing point, and therefore the compound having a good compatibility at a low temperature is preferred.
A variety of liquid crystal compounds have so far been prepared. Development of a new liquid crystal compound is continued even now because excellent physical properties that are not found in conventional compounds are expected. The reason is that a suitable balance between two of physical properties required upon preparing the liquid crystal composition is expected for the new compound. Only limited examples of reports are found on the compound having a divalent group described below.

JP 2008-545669 A discloses a compound having No. 36 on page 39. The compound is also disclosed on page 41 in JP 2009-507759 A.

JP 2008-545671 A discloses a mixture of isomers of 5-(4-ethoxy-2,3-difluorophenyl)-2-pentyldihydro-2H-pyran as a synthetic intermediate on page 18.

JP 2004-352722 A discloses compound (B1.2 No. 11) on page 100, and compound (B4.1 No. 7) on page 107.
